U.S. Pat. Nos. 2,154,280 and 2,748,597 to Nadai et al and Kooistra, respectively, disclose testing materials under increased temperature by employing a covering furnace.
U.S. Pat. No. 2,290,868 to Eriksson is concerned with a tensile strength apparatus that employs a covering furnace with an oval-like cross section for receiving the test specimen.
U.S. Pat. No. 2,375,032 to Park et al and U.S. Pat. No. 3,176,499 to Sikora described tensile testing apparatus with covering furnaces that employ lines or pipes to feed an inert gas or means to evacuate the chamber.